1. Field of the Invention
The present invention relates to a method and apparatus for expanding tobacco by spray impregnating cut tobacco particles in a pressure vessel with liquid and gaseous carbon dioxide following which the impregnated tobacco particles are heated to effect rapid release of the carbon dioxide with corresponding expansion of the particles.
2. Description of the Prior Art
The tobacco art has long recognized the need to effect the greatest possible degree of expansion of tobacco while maintaining desirable handling and smoking characteristics. Correspondingly, numerous attempts have been made in the art to effect such expansion of tobacco, frequently by treatment of the tobacco with an agent which expands greatly during evaporation or after a decrease in pressure.
One attempt in the prior art to expand tobacco is disclosed in U.S. Pat. No. 1,789,435 wherein a method is described for expanding the volume of tobacco in order to make up the loss of weight caused in curing the tobacco leaf. The tobacco is contacted with a gas such as air, carbon dioxide, or steam under pressure and, upon release of the pressure, the tobacco tends to expand limitedly between 5% and 15% by volume.
Prior art disclosures are also available which teach that tobacco may be expanded by addition of water to the tobacco which causes the tobacco to swell following which the contained moisture is evaporated to set the expansion.
Another attempt to expand tobacco has been by use of carbohydrates as a means to improve puffing of tobacco stems. In this process the tobacco stems are soaked in an aqueous solution of carbohydrate following which they are heated to set the tobacco expansion.
Volatile organic liquids have also been disclosed in the prior art as means to effect expansion of tobacco.
Methods have also been proposed in the prior art to effect tobacco expansion by use of ammonia and carbon dioxide gases. Carbon dioxide has also been used in the liquid state as a means of expanding tobacco and other organic substances. Typically, such processes require immersing the organic substance or tobacco in a pool of liquid carbon dioxide wherein tobacco particles are steeped in the liquid carbon dioxide following which the tobacco particles are heated, preferably using super-heated steam to effect expansion. These methods, however, invite various disadvantages by requiring large quantities of liquid carbon dioxide relative to the amount of carbon dioxide which is impregnated within the tobacco particles. Furthermore, components of the tobacco such as flavoring materials may be extracted by the use of excess liquid carbon dioxide.
Although numerous attempts have been made in the prior art to expand tobacco by various means, these attempts have achieved limited success by either requiring expanding agents which have been alleged to cause environmental pollution or are otherwise costly or cumbersome to operate. It has now been found that, by practice of the present invention, tobacco may be expanded by means of liquid carbon dioxide in a simple, efficient and highly economical manner.